Gas turbine engines employ sealing devices in various capacities in order to restrict a flow of fluid or gas from one portion of the engine to another. For example, sealing devices, such as finger seals, may be used to separate a primary engine flowpath from a secondary flowpath, where the primary engine flowpath directs the flow of gases to compressor and turbine stages of the engine, and the secondary flowpath delivers compressed air throughout the engine for performing a variety of functions. Leakage of compressed air from the secondary flowpath into the primary engine flowpath may adversely affect the performance of certain engine functions, such as the cooling of individual components, the provision of a bleed air source, the control of ventilation among engine cavities and structures, and the like. In another example, finger seals may be used to separate the secondary flowpath from engine cavities containing fluids such as lubricating oil, so that bleed air taken from the secondary flowpath does not contaminate air supplied to an aircraft's environmental control system. In this regard, sealing devices may be mounted adjacent to lubricated bearings and engine oil sumps.
Generally, finger seals comprise a plurality of diaphragm members, each having one end fixed to a stationary body of the engine and another end that sealingly engages a seal rotor. Each diaphragm member, which may be disk-shaped, includes a set of flexible members or fingers along its sealing perimeter. The fingers are integrally formed as part of the corresponding diaphragm members. The diaphragm members may be stacked to form laminates, and each set of fingers of each diaphragm member makes up a layer of fingers. To prevent leakage across the seal, two or more layers of fingers are relatively positioned such that gaps between fingers in one of the diaphragm members are blocked by the fingers of an adjacent diaphragm member.
The finger seal may form an inner diameter riding seal. In such case, during engine operation, the fingers deform in a generally radially outward direction due to various factors including centrifugal and thermal growth of the rotating surface. The reverse is true with a finger seal that forms an outer diameter riding seal. Here, centrifugal and thermal growth causes the rotor to move away from the seal. In order to maintain an effective seal in either design, the fingers restore themselves radially towards the rotating surface as it changes its size. However, as the demand for improved engine efficiency increases, engine speeds may increase resulting in an increase of pressure differential across the seal. As a result, fluid pressure acting on the radially deformed fingers may increase. Additionally, the fluid pressure distribution may cause increased pressure loading on one or more layers of fingers, which in turn can cause these higher loaded flexible members to experience greater deflection than flexible members from the adjacent layers of fingers. This difference in relative deflection between adjacent layers of fingers can cause gaps between individual fingers to shift relative to an overlapping finger of an adjacent layer of fingers. Due to this relative shift from one layer to the next, the gaps may not be suitably blocked by the fingers of the adjacent diaphragm member, and leakage may occur across the seal. Consequently, the effectiveness of the seal may be reduced.
Accordingly, it is desirable to have an improved sealing device for use between stationary and rotating surfaces. In addition, it is desirable for the sealing device to be relatively simple and inexpensive to manufacture. Moreover, it is desirable for the sealing device to be capable of being retrofitted into engines, which currently include conventional finger seals. Furthermore, other desirable features and characteristics of the inventive subject matter will become apparent from the subsequent detailed description of the inventive subject matter and the appended claims, taken in conjunction with the accompanying drawings and this background of the inventive subject matter.